Subquery mysql with where clause - mysql

Question

Hello, Im stuck with mysql subquery, this is the table I have
table detail_order
==============================
id_detail | id_order | id_toko
1 | 1 | 1
2 | 1 | 2
3 | 1 | 3
4 | 1 | 4
table ket_detail
==================================
id_ket | id_detail | id_size | qty
1 | 1 | 7 | 3
2 | 1 | 9 | 1
3 | 1 | 5 | 2
4 | 2 | 7 | 8
table size
=================================
id_size | size | id_color | stock
7 | 40 | 6 | 30
9 | 42 | 6 | 20
5 | 39 | 5 | 30
table color
==========================
id_color | color
6 | green
5 | red
Im trying in subquery to show qty on table ket_detail with where clause, but when Im try it subquery return more than one row.
this is my query
SELECT dt.id_detail,
SUM(tk.qty) AS tot_order,
COUNT(dm.color) AS tot_color,
(SELECT ket.qty FROM ket_detail AS ket, t_size AS u
WHERE u.id_size=ket.id_size AND u.size = 40) AS size_40
FROM detail_order AS dt
LEFT JOIN ket_detail AS tk ON tk.id_detail=dt.id_detail
LEFT JOIN t_size AS u ON u.id_size = tk.id_size
LEFT JOIN t_color AS dm ON dm.id_color=u.id_color
WHERE dt.id_order = 1
GROUP BY dt.id_detail
but when I change size to 39 the data like this
id_detail | tot_order | tot_color | size_40
============================================
1 | 6 | 2 | 2
2 | 8 | 1 | 2
3 | NULL | 0 | 2
4 | NULL | 0 | 2
what do I want is the data like this
id_detail | tot_order | tot_color | size_40
============================================
1 | 6 | 2 | 3
2 | 8 | 1 | 8
3 | NULL | 0 | NULL
4 | NULL | 0 | NULL

Answer 1

You don't need a subquery to get the size = 39 or size = 40 data. You can use conditional aggregation instead:
SELECT dt.id_detail,
SUM(tk.qty) AS tot_order,
COUNT(dm.color) AS tot_color,
SUM(CASE
WHEN u.size = 39 THEN tk.qty
ELSE 0
END) AS size_39,
SUM(CASE
WHEN u.size = 40 THEN tk.qty
ELSE 0
END) AS size_40
FROM detail_order AS dt
LEFT JOIN ket_detail AS tk ON tk.id_detail=dt.id_detail
LEFT JOIN t_size AS u ON u.id_size = tk.id_size
LEFT JOIN t_color AS dm ON dm.id_color=u.id_color
WHERE dt.id_order = 1
GROUP BY dt.id_detail;
Demo here
The proper way to do it with a subquery is:
SELECT dt.id_detail,
SUM(tk.qty) AS tot_order,
COUNT(dm.color) AS tot_color,
(SELECT SUM(ket.qty)
FROM ket_detail AS ket
JOIN t_size AS u ON u.id_size=ket.id_size
WHERE ket.id_detail = dt.id_detail AND u.size = 40) AS size_40
FROM detail_order AS dt
LEFT JOIN ket_detail AS tk ON tk.id_detail=dt.id_detail
LEFT JOIN t_size AS u ON u.id_size = tk.id_size
LEFT JOIN t_color AS dm ON dm.id_color=u.id_color
WHERE dt.id_order = 1
GROUP BY dt.id_detail;
Demo here
If you need to select the total quantity for more than one sizes, then you have to repeat the subquery for each required size. Hence, I think, the first query provides a solution that is cleaner, easier to extend and more efficient.